In a typical power distribution network, substations deliver electrical power to consumers via interconnected cables and electrical apparatuses. The cables terminate on bushings passing through walls of metal encased equipment, such as capacitors, transformers, and switchgear. Increasingly, this equipment is “dead front,” meaning that the equipment is configured such that an operator cannot make contact with any live electrical parts. Dead front systems have proven to be safer than “live front” systems, with comparable reliability and low failure rates.
Various safety codes and operating procedures for underground power systems require a visible disconnect between each cable and electrical apparatus to safely perform routine maintenance work, such as line energization checks, grounding, fault location, and hi-potting. A conventional approach to meeting this requirement for a dead front electrical apparatus is to provide a “separable connector system” including a first connector assembly connected to the apparatus and a second connector assembly connected to an electric cable. The second connector assembly is selectively positionable with respect to the first connector assembly. An operator can engage and disengage the connector assemblies to achieve electrical connection or disconnection between the apparatus and the cable.
Generally one of the connector assemblies includes a female connector, and the other of the connector assemblies includes a corresponding male connector. In some cases, each of the connector assemblies can include two connectors. For example, one of the connector assemblies can include ganged, substantially parallel female connectors, and the other of the connector assemblies can include substantially parallel male connectors that correspond to and are aligned with the female connectors. During a typical electrical connection operation, an operator slides the female connector(s) over the corresponding male connector(s).
Each female connector includes a recess from which a male contact element or “probe” extends. Each male connector includes a contact assembly configured to at least partially receive the probe when the female and male connectors are connected. A conductive shield housing is disposed substantially around the contact assembly, within an elongated insulated body composed of elastomeric insulating material. The shield housing acts as an equal potential shield around the contact assembly. A non-conductive nose piece is secured to an end of the shield housing and provides insulative protection for the shield housing from the probe. The nosepiece is attached to the shield housing with threaded or snap-fit engagement.
Air pockets tend to emerge in and around the threads or snap-fit connections. These air pockets provide paths for electrical energy and therefore may result in undesirable and dangerous electrical discharge and device failure. In addition, sharp edges along the threads or snap-fit connections are points of high electrical stress that can alter electric fields during loadbreak switching operation, potentially causing electrical failure and safety hazards.
One conventional approach to address these problems is to replace the shield housing and nose piece with an all-plastic sleeve coated with a conductive adhesive. The sleeve includes an integral nose piece. Therefore, there are no threaded or snap-fit connections in which air pockets may be disposed. However, air pockets tend to exist between the sleeve and the conductive adhesive. In addition, there is high manufacturing cost associated with applying the conductive adhesive to the sleeve.
Therefore, a need exists in the art for a cost-effective and safe connector system. In particular, a need exists in the art for a cost-effective separable connector shield housing with reduced potential for electrical discharge and failure.